High-electron-mobility transistor

ABSTRACT

A high-electron-mobility transistor (HEMT) device includes a plurality of semiconductor layers formed on a substrate, wherein a two-dimensional electron gas (2DEG) layer is formed in the semiconductor layers; an etch-stop layer formed on the plurality of semiconductor layers; a p-type semiconductor layer pattern formed on the etch-stop layer; and a gate electrode formed on the p-type semiconductor layer pattern.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 from Korean PatentApplication No. 10-2013-0025251, filed on Mar. 8, 2013, in the KoreanIntellectual Property Office, the disclosure of which is incorporatedherein in its entirety by reference.

BACKGROUND

The present inventive concepts relate to a high-electron-mobilitytransistor (HEMT) device, and more particularly, to a HEMT device thathas a “normally off” characteristic.

In order to use as a transistor for a power device that obtains a highbreakdown voltage and fast response speeds, a study on ahigh-electron-mobility transistor (HEMT) has been actively conducted. AnHEMT device includes semiconductor layers with different electricalpolarization characteristics, and a semiconductor layer with relativelygreat polarizability in the HEMT device may cause another semiconductorlayer bonded heterogeneously thereto to have two-dimensional electrongas (2DEG), i.e., a gas of electrons free to move in two dimensions buttightly confined in the third dimension. The 2DEG may serve as a channelbetween a drain electrode and a source electrode, and currents flowingin the channel may be controlled by a bias voltage applied to a gateelectrode. A conventional HEMT device, e.g., an HEMT device using aheterogeneous junction by a group III-nitride semiconductor, has a“normally on” characteristic and has high power consumption due to sucha normally on characteristic.

SUMMARY

The inventive concepts provide a high-electron-mobility transistor witha stable normally off characteristic.

According to an aspect of the inventive concepts, there is provided ahigh-electron-mobility transistor device, including a plurality ofsemiconductor layers formed on a substrate, wherein a two-dimensionalelectron gas (2DEG) layer is formed in the semiconductor layers;etch-stop layers formed on the plurality of semiconductor layers; ap-type semiconductor layer pattern formed on the etch-stop layer; and agate electrode formed on the p-type semiconductor layer pattern.

The plurality of semiconductor layers may include a first semiconductorlayer and a second semiconductor layer that are sequentially formed onthe substrate, and the 2DEG region may be formed in a part of the firstsemiconductor layer adjacent to an interface between the firstsemiconductor layer and the second semiconductor layer.

The 2DEG region may be omitted from a part of the first semiconductorlayer that overlaps with the p-type semiconductor layer pattern.

The second semiconductor layer may include a material having band gapenergy higher than that of the first semiconductor layer.

The first semiconductor layer may include gallium nitride, and thesecond semiconductor layer may include aluminum gallium nitride.

The p-type semiconductor layer pattern may include gallium nitride dopedwith p-type impurities or aluminum gallium nitride doped with p-typeimpurities.

The etch-stop layer may be in contact with an entire bottom surface ofthe p-type semiconductor layer pattern.

The etch-stop layer may include silicon carbon nitride (SixCl_(1-x)N),where 0≦x≦1.

The high-electron-mobility transistor device may further include a holeinjection layer between the etch-stop layer and the second semiconductorlayer.

The high-electron-mobility transistor device may further include ann-type semiconductor layer between the p-type semiconductor layerpattern and the gate electrode.

According to another aspect of the inventive concepts, there is provideda high-electron-mobility transistor device, including a channel layerformed on a substrate; a channel-supplying layer formed on the channellayer; an etch-stop layer formed on the channel-supplying layer; ap-type semiconductor layer pattern formed on a part of the etch-stoplayer; and a gate electrode on the p-type semiconductor layer pattern.

The etch-stop layer may be formed on an entire top surface of thechannel-supplying layer.

The high-electron-mobility transistor device may further include asource electrode and a drain electrode that pass through the etch-stoplayer and the channel-supplying layer and are connected to the channellayer.

The gate electrode may be formed to vertically overlap with the p-typesemiconductor layer pattern.

The p-type semiconductor layer pattern may have a shape corresponding tothat of the gate electrode.

According to another aspect of the inventive concepts, a radio frequencypower amplifier module includes a power amplifier module including atleast one high electron mobility transistor (HEMT), as described above;a transceiver coupled with the power amplifier module and configured toreceive an input signal and to transmit the input signal to the poweramplifier module, wherein the power amplifier module is configured toamplify the input signal received from the transceiver; and an antennaswitch module coupled with the power amplifier module and including anantenna structure, wherein the antenna switch module is configured toreceive the amplified input signal from the power amplifier module andto transmit the amplified input signal over the air via the antennastructure.

The antenna switch module of the RF power amplifier may also beconfigured to receive the input signal through the antenna structure andto transmit the input signal to the transceiver.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the inventive concepts will be more clearlyunderstood from the following detailed description taken in conjunctionwith the accompanying drawings in which:

FIG. 1 is a cross-sectional view of a high-electron-mobility transistor(HEMT) device according to an exemplary embodiment;

FIG. 2 is a schematic band diagram of an HEMT device employing a p-typesemiconductor layer pattern;

FIG. 3 is a cross-sectional view of an HEMT device according to anexemplary embodiment;

FIG. 4 is a cross-sectional view of an HEMT device according to anexemplary embodiment;

FIG. 5 is a cross-sectional view of an HEMT device according to anexemplary embodiment;

FIG. 6 is a cross-sectional view of an HEMT device according to anexemplary embodiment;

FIG. 7A to 7F are cross-sectional views related to a method offabricating an HEMT device, according to an exemplary embodiment; and

FIG. 8 is a schematic diagram of a power module system employing anHEMT, according to an exemplary embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Exemplary embodiments of the present inventive concepts will bedescribed in detail with reference to the accompanying drawings. As usedherein, the term “and/or” includes any and all combinations of one ormore of the associated listed items. Expressions such as “at least oneof,” when preceding a list of elements, modify the entire list ofelements and do not modify the individual elements of the list.

The inventive concepts may, however, be embodied in many different formsand should not be construed as being limited to the embodiments setforth herein; rather, these embodiments are provided so that thisdisclosure will sufficiently describe and enable the concepts of theinvention to those skilled in the art. In the drawings, the thickness orsize of each layer is exaggerated for convenience of description andclarity.

FIG. 1 is a cross-sectional view of a high-electron-mobility transistor(HEMT) device 100 according to an exemplary embodiment.

Referring to FIG. 1, the HEMT device 100 may include a substrate 110, abuffer layer 115, a high-resistance semiconductor layer 120, a channellayer 130, a channel-supplying layer 140, an etch-stop layer 150, ap-type semiconductor layer pattern 160, a source electrode 182, a drainelectrode 184, and a gate electrode 186.

The substrate 110 may be a sapphire substrate, a silicon carbidesubstrate, a gallium nitride substrate, a silicon substrate, a germaniumsubstrate, an aluminum nitride substrate, etc. For example, asingle-crystal silicon carbide substrate with high thermal conductivitymay be used as the substrate 110.

The buffer layer 115 may be formed on the substrate 110. The bufferlayer 115 may work as a stress alleviating region that alleviates stressgenerated due to a lattice constant difference between the substrate 110and the high-resistance semiconductor layer 120 or defects such asmisfit dislocations generated due to the lattice constant difference. Inexemplary embodiments, the buffer layer 115 may include gallium nitride,aluminum nitride, aluminum gallium nitride, silicon carbon nitride, orcombinations thereof.

Although not shown, a superlattice layer (not shown) that has amulti-layer structure of aluminum nitride/gallium nitride/aluminumnitride/gallium nitride may be further formed between the substrate 110and the buffer layer 115. In addition, a stacked structure which aplurality of aluminum gallium nitride, Al_(x)Ga_(1-x)N layers, withdifferent content forms may be further included. In addition, aplurality of protrusions (not shown) may be further formed between thesubstrate 110 and the buffer layer 115.

The high-resistance semiconductor layer 120 may be formed on the bufferlayer 115. In exemplary embodiments, the high-resistance semiconductorlayer 120 may be a semi-insulating layer having high resistance. In thiscase, when electrons move in the channel layer 130 formed on thehigh-resistance semiconductor layer 120, leakage of currents through thehigh-resistance semiconductor layer 120 may be avoided. Electronmobility in the channel layer 130 may be increased, thereby decreasingan on-resistance of the HEMT device 100. In this case, the on-resistanceindicates a resistance between the source electrode 182 and the drainelectrode 184 when a voltage is applied to the gate electrode 186.

For example, the high-resistance semiconductor layer 120 may include agallium nitride layer having a sheet resistance of about 10⁷ Ωcm⁻² to10¹¹ Ωcm⁻², but the high-resistance semiconductor layer 120 is notlimited thereto. In exemplary embodiments, the high-resistancesemiconductor layer 120 may be an undoped gallium nitride layer or agallium nitride layer doped with dopants, such as magnesium (Mg), zinc(Zn), carbon (C), iron (Fe), etc.

The channel layer 130 may be formed on the high-resistance semiconductorlayer 120. The channel layer 130 may include at least one of thefollowing various materials: aluminum nitride, gallium nitride, indiumnitride, indium gallium nitride, aluminum gallium nitride, aluminumindium nitride, etc. However, the material of the channel layer 130 isnot limited thereto and any material layer in which a two-dimensionalelectron gas (2DEG) may be formed may be used. The channel layer 130 maybe an undoped semiconductor layer, but in some cases, the channel layer130 may be a semiconductor layer in which a given dopant is doped. Forexample, the channel layer 130 may be an undoped gallium nitride layer.For example, the thickness of the channel layer 130 may be in a range ofabout 10 nm to about 100 nm.

The channel-supplying layer 140 may be formed on the channel layer 130.The channel-supplying layer 140 may include a semiconductor materialhaving a band gap energy higher than that of the channel layer 130. Inexemplary embodiments, the channel-supplying layer 140 may have a singlelayered or multi-layered structure that includes one or more materialsthat are selected from nitrides including at least one of aluminum,gallium, and indium. In exemplary embodiments, the channel-supplyinglayer 140 may be an undoped aluminum gallium nitride layer. For example,the channel-supplying layer 140 may be an Al_(x)Ga_(1-x)N layer, where0≦x≦1, or an Al_(x)Ga_(1-x)N layer, where 0.15≦x≦0.6. Thechannel-supplying layer 140 may have a thickness of about 20 nm to about50 nm.

A 2DEG region may be formed in a part of the channel layer 130 near aninterface between the channel layer 130 and the channel-supplying layer140. When there is a hetero-structure in which the channel layer 130 andthe channel-supplying layer 140 are gallium nitride and aluminum galliumnitride, respectively, the 2DEG region may be formed at III-V nitridelayers (that is, at a gallium nitride layer and at an aluminum galliumnitride layer) by spontaneous polarization and piezo polarization due totensile strain. The 2DEG region may work as a current passage betweenthe source electrode 182 and the drain electrode 184 (i.e., as a channelregion).

The etch-stop layer 150 may be formed on the channel-supplying layer 140and may cover an entire top surface of the channel-supplying layer 140.

If the etch-stop layer 150 is not formed on the channel-supplying layer140, the p-type semiconductor layer pattern 160 is formed directly onthe channel-supplying layer 140. In this case, an upper surface of thechannel-supplying layer 140 may be damaged in the process of forming thep-type semiconductor layer pattern 160. For example, if an etchingprocess is performed in the process of forming the p-type semiconductorlayer pattern 160, the upper surface of the channel-supplying layer 140may be directly exposed to etchant and thus the upper surface of thechannel-supplying layer 140 may be damaged. Thus, a surface trap density(at which electrons are trapped on the upper surface of thechannel-supplying layer 140 in an on-state) may increase. As a result, acurrent collapse may occur where an on-resistance sharply increases as avoltage applied to the drain electrode 184 increases. However, since theetch-stop layer 150 is formed on the channel-supplying layer 140, thepresent embodiment may prevent damage to the upper surface of thechannel-supplying layer 140 in the process of forming the p-typesemiconductor layer pattern 160. Thus, the current collapse may beminimized.

In addition, the etch-stop layer 150 may form a stable interface withrespect to the upper surface of the channel-supplying layer 140. Theetch-stop layer 150 may function as a passivation layer that protectsthe surface of the channel-supplying layer 140; and, thus, the leakageof currents due to the surface trap of the channel-supplying layer 140may be avoided, thereby decreasing an on-resistance of the HEMT device100.

The etch-stop layer 150 may include a material having an etchselectivity with respect to the p-type semiconductor layer pattern 160.In exemplary embodiments, the etch-stop layer 150 may include siliconcarbon nitride (Si_(x)C_(1-x)N, 0≦x≦1). In the process of etching toform the p-type semiconductor layer pattern 160, it may be difficult toaccurately control an etch thickness of the p-type semiconductor layerpattern 160 since both the p-type semiconductor layer pattern 160 andthe channel-supplying layer 140 include nitride materials. The presentinventive concepts include the etch-stop layer 150 between the p-typesemiconductor layer pattern 160 and the channel-supplying layer 140;and, thus, the channel-supplying layer 140 under the etch-stop layer 150may be rarely affected even if the p-type semiconductor layer pattern160 is sufficiently etched. Thus, it may be easy to control etchthickness of the p-type semiconductor layer pattern 160; andfluctuations in on-resistance and fluctuations in threshold voltage ofthe HEMT device due to the inaccurate etch thickness of the p-typesemiconductor layer pattern 160 may be avoided.

In exemplary embodiments, the etch-stop layer 150 may have a thicknessof about 1 nm to 100 nm. When the thickness of the etch-stop layer 150is less than 1 nm, the channel-supplying layer 140 may not besufficiently protected in the etching process of the p-typesemiconductor layer pattern 160. When the thickness of the etch-stoplayer 150 is larger than 100 nm, the performance of the HEMT device 100may be affected by the etch-stop layer 150.

The p-type semiconductor layer pattern 160 may be formed on a part ofthe etch-stop layer 150. Since the p-type semiconductor layer pattern160 is formed to have a width that is less than that of the etch-stoplayer 150, the p-type semiconductor layer pattern 160 may be formed sothat its entire bottom is in contact with the etch-stop layer 150.

The p-type semiconductor layer pattern 160 may be formed between thegate electrode 186 and the channel-supplying layer 140 to implement anormally off characteristic. The normally off characteristic indicates acharacteristic that is in an off state when a voltage is not applied tothe gate electrode 186 (i.e., in a normal mode), and that is in an onstate when a voltage is applied to the gate electrode 186. The p-typesemiconductor layer pattern 160 may form a depletion region in the 2DEGregion formed in the channel layer 130 so that a discontinuous 2DEGregion section may be formed in the channel layer 130 between the sourceelectrode 182 and the drain electrode 184. For example, the 2DEG regionmay not be formed in a portion of the channel layer 130 under the p-typesemiconductor layer pattern 160.

For example, FIG. 2 shows a schematic band diagram that is exhibited bya structure in which the gate electrode 186, the p-type semiconductorlayer pattern 160, the channel-supplying layer 140, and the channellayer 130 are stacked. FIG. 2 illustratively represents a band diagramwhen the p-type semiconductor layer pattern 160 is a p-doped AlGaNlayer, the channel-supplying layer 140 is an undoped AlGaN layer (anintrinsic AlGaN layer), and the channel layer 130 is an undoped GaNlayer (an intrinsic GaN layer). The level of an energy band around thechannel-supplying layer 140 may rise by p-n junction, which is made whenthe p-type semiconductor layer pattern 160 is formed between thechannel-supplying layer 140 and the gate electrode 186. While a bias isnot applied to the gate electrode 186, a depletion region may be formedat the channel layer 130 under the gate electrode 186, and a 2DEG regionmay thus be depleted because a conduction band (E_(C)) is formed morehighly than the Fermi level (E_(F)) at the regions between the channellayer 130 and the gate electrode 186. Thus, the 2DEG region may not beformed at the channel layer 130 under the p-type semiconductor layerpattern 160; and a normally off structure in which current does not flowin the absence of a bias applied to the gate electrode 186 may berealized.

In exemplary embodiments, the p-type semiconductor layer pattern 160 mayhave a thickness of about 10 nm to about 200 nm. When the thickness ofthe p-type semiconductor layer pattern 160 is less than 10 nm, thenormally on characteristic, wherein a current flows in an off state, maybe expressed because the depletion region is not sufficiently formed inthe 2DEG region of the channel layer 130. When the thickness of thep-type semiconductor layer pattern 160 is larger than 200 nm, the bandgap energy of the channel-supplying layer 140 under the p-typesemiconductor layer pattern 160 may excessively rise by the p-typesemiconductor layer pattern 160; and, thus, the bias voltage needed tobe applied to the gate electrode 186 to establish an on state may beexcessively increased.

In exemplary embodiments, the p-type semiconductor layer pattern 160 mayinclude gallium nitride, aluminum gallium nitride, etc., and may includedopants, such as Mg, Zn, Be, etc., at a doping concentration of about1×10¹⁷/cm³ to 1×10²²/cm³.

A first passivation layer 174 may be formed on the etch-stop layer 150in a shape that surrounds the sidewalls of the p-type semiconductorlayer pattern 160, and a second passivation layer 176 may be formed onthe first passivation layer 174. The first passivation layer 174 and thesecond passivation layer 176 may include silicon oxide, silicon nitride,silicon oxynitride, etc. The first passivation layer 174 and the secondpassivation layer 176 may include the same material or differentmaterials.

The source electrode 182 and the drain electrode 184 may be formed sothat they both pass through the first and second passivation layers 174and 176, through the etch-stop layer 150, and through thechannel-supplying layer 140. The source electrode 182 and the drainelectrode 184 may be connected to the channel layer 130. The channellayer 130 is between the source electrode 182 and the drain electrode184 and has a 2DEG region therein and may function as a channel regionof the HEMT device 100.

The gate electrode 186 may be formed on the p-type semiconductor layerpattern 160 between the source electrode 182 and the drain electrode184. A bottom surface of the gate electrode 186 may be in contact with atop surface of the p-type semiconductor layer pattern 160. Although FIG.1 shows that the gate electrode 186 is formed to have a shape withsubstantially the same width as that of the p-type semiconductor layerpattern 160, the width of the gate electrode 186 may be formed to beless than that of the p-type semiconductor layer pattern 160.

According to the present inventive concepts, since the etch-stop layer150 is interposed between the channel-supplying layer 140 and the p-typesemiconductor layer pattern 160, damages to the surface of thechannel-supplying layer 140 may be avoided in the etching process of thep-type semiconductor layer pattern 160, thereby decreasing the leakageof currents. In addition, accurate control of the thickness of thep-type semiconductor layer pattern 160 may be easily established; and,thus, the HEMT device 100 may have a stable normally off characteristic.

FIG. 3 is a cross-sectional view of an HEMT device 100 a according to anexemplary embodiment. The HEMT device 100 a is similar to the HEMTdevice 100 that has been described with reference to FIG. 1, except thatit further includes an n-type semiconductor layer 162.

Referring to FIG. 3, the HEMT device 100 a may further include then-type semiconductor layer 162 between the p-type semiconductor layerpattern 160 and the gate electrode 186. The n-type semiconductor layer162 may completely cover a top surface of the p-type semiconductor layerpattern 160. The n-type semiconductor layer 162 may prevent current fromleaking from the gate electrode 186 to the p-type semiconductor layerpattern 160. The n-type semiconductor layer 162 may include aluminumnitride, gallium nitride, aluminum gallium nitride, indium nitride,aluminum indium nitride, indium gallium nitride, aluminum indium galliumnitride, etc., and an n-type dopant, such as silicon (Si), germanium(Ge), tin (Sn), etc., may be doped in the n-type semiconductor layer 162at a given concentration.

FIG. 4 is a cross-sectional view of an HEMT device 100 b according to anexemplary embodiment. The HEMT device 100 b is similar to the HEMTdevice 100 that has been described with reference to FIG. 1, except thatit further includes a hole injection layer 164.

Referring to FIG. 4, the HEMT device 100 b may further include the holeinjection layer 164 between the channel-supplying layer 140 and theetch-stop layer 150. The hole injection layer 164 may include a materialwith a band gap energy different from that of the channel-supplyinglayer 140. The hole injection layer 164 may prevent currents fromleaking from the gate electrode 186 to the channel-supplying layer 140because it forms an energy barrier with respect to the channel-supplyinglayer 140. For example, the hole injection layer 164 may include a GaNmaterial doped with a p-type dopant, but the material of the holeinjection layer 164 is not limited thereto; and the hole injection layer164 may include a p-type semiconductor material having a band gap energydifferent from that of the channel-supplying layer 140.

The hole injection layer 164 may completely cover the top of thechannel-supplying layer 140. For example, the hole injection layer 164may have a thickness of 20 nm or less. When the thickness of the holeinjection layer 164 is too large, the conduction band level of thechannel layer 130 may rise so that an electron density near an interfacebetween the channel layer 130, in which a 2DEG region may be formed; andthe channel-supplying layer 140 may be decreased, thereby increasing theon-resistance between the source electrode 182 and the drain electrode184. Thus, the thickness of the hole injection layer 164 may be lessthan or equal to a critical thickness that does not influence the 2DEGin the channel layer 130 under the hole injection layer 164; and the2DEG region may be formed in portions of the channel layer 130 betweenthe source electrode 182 and the drain electrode 184.

FIG. 5 is a cross-sectional view of an HEMT device 100 c according to anexemplary embodiment. The HEMT device 100 c is similar to the HEMTdevice 100 that has been described with reference to FIG. 1, except forthe shapes of a source electrode 182 a and a drain electrode 184 a.

Referring to FIG. 5, the source electrode 182 a and the drain electrode184 a may be formed so that they both pass through the first passivationlayer 174, the second passivation layer 176, and the etch-stop layer 150and are connected to the channel-supplying layer 140.

In this case, the channel-supplying layer 140 may be etched by a giventhickness from the top, and the source electrode 182 a and the drainelectrode 184 a may be placed on the etched region. Alternatively,unlike FIG. 5, the upper portion of the channel-supplying layer 140 maynot be etched and the source electrode 182 a and the drain electrode 184a may be formed on the non-etched top of the channel-supplying layer140.

FIG. 6 is a cross-sectional view of an HEMT device 100 d according to anexemplary embodiment. The HEMT device 100 d is similar to the HEMTdevice 100 that has been described with reference to FIG. 1, except thatit may not include a substrate and a buffer layer.

Referring to FIG. 6, the HEMT device 100 d may optionally include asubstrate 110 and a buffer layer 115. For example, it is possible tofabricate the HEMT device 100 d and then remove the substrate 110 orboth the substrate 110 and the buffer layer 115. Thus, the HEMT device100 d may not include the substrate 110 and/or the buffer layer 115.

FIG. 7A to 7F are cross-sectional views of a method of fabricating anHEMT device, according to an exemplary embodiment. The fabricatingmethod may be a method of fabricating the HEMT device 100 that isdescribed with reference to FIG. 1.

Referring to FIG. 7A, the buffer layer 115 may be formed on thesubstrate 110. In exemplary embodiments, the buffer layer 115 mayinclude gallium nitride. For example, the buffer layer 115 may be formedon the substrate 110 by a molecular beam epitaxy (MBE) process, ahydride vapor phase epitaxy (HVPE) process, or a metal-organic vaporphase epitaxy (MOVPE) process. The buffer layer 115 may include, e.g.,aluminum nitride, aluminum gallium nitride, silicon carbon nitride,etc., but the material of the buffer layer 115 is not limited thereto.

The high-resistance semiconductor layer 120 may be formed on the bufferlayer 115. The high-resistance semiconductor layer 120 may includegallium nitride. The high-resistance semiconductor layer 120 may beformed by an in-situ doping of dopants, such as Mg, Zn, C, Fe, etc., ina process of forming the gallium nitride layer. Alternatively, thehigh-resistance semiconductor layer 120 may be grown at a lowtemperature of about 500° C. to 600° C. Thus, the high-resistancesemiconductor layer 120 may have a sheet resistance in a range of about10⁷ Ωcm⁻² to 10¹¹ Ωcm².

The channel layer 130 may be formed on the high-resistance semiconductorlayer 120 and may include an undoped gallium nitride layer and be formedto have a thickness of about 10 nm to 100 nm.

Subsequently, the channel-supplying layer 140 may be formed on thechannel layer 130. The channel-supplying layer 140 may include asemiconductor material having a band gap energy higher that that of thechannel layer 130. As a hetero-structure including the channel layer 130and the channel-supplying layer 140 is formed, a 2DEG region may beformed in the channel layer 130.

Referring to FIG. 7B, the etch-stop layer 150 may be formed on thechannel-supplying layer 140. The etch-stop layer 150 may be formed tohave a thickness in a range of about 1 nm to 100 nm. For example, theetch-stop layer 150 may be formed to have a thickness of about 10 nm.The etch-stop layer 150 may include silicon carbon nitride(Si_(x)C_(1-x)N, 0≦x≦1) and be formed by an MBE process, an MOVPEprocess, an HYPE process, etc. The etch-stop layer 150 may be formed insitu in the process of forming the channel-supplying layer 140.Alternatively, the etch-stop layer 150 may be formed in a processseparate from the process of forming the channel-supplying layer 140.

Referring to FIG. 7C, a p-type semiconductor layer 160 a may be formedon the etch-stop layer 150. The p-type semiconductor layer 160 a may beformed to have a thickness of about 10 nm to 100 nm. The p-typesemiconductor layer 160 a may include gallium nitride, aluminum galliumnitride, etc., and may include a dopant, such as Mg, Zn, Be, etc., at adoping concentration of about 1×10¹⁷/cm³ to 1×10²²/cm³.

As the p-type semiconductor layer 160 a is formed on thehetero-structure of the channel-supplying layer 140 and the channellayer 130, the conduction band level of the channel layer 130 may beraised so that a 2DEG region may not be formed in the channel layer 130.

Referring to FIG. 7D, the p-type semiconductor layer 160 a may bepatterned to form the p-type semiconductor layer pattern 160. Forexample, a photoresist layer (not shown) may be formed on a portion ofthe p-type semiconductor layer 160 a; and only a portion of the p-typesemiconductor layer 160 a on which the photoresist layer is not disposedmay be exposed. The exposed portion of the p-type semiconductor layer160 a may be removed using the photoresist layer as a mask until anupper surface of the etch-stop layer 150 is exposed.

In exemplary embodiments, the patterning process may be a dry etchingprocess. For example, a dry etching process—in which a gas includingchlorine (Cl₂) and/or boron trichloride (BCl₃) is used as etchant—may beperformed, but the kind of the etching process is not limited thereto.

The etch-stop layer 150 may include a material having etch selectivitywith respect to the p-type semiconductor layer 160 a. For example, whenusing an etchant to pattern the p-type semiconductor layer 160 a, theetching rate of the etch-stop layer 150 may be lower than that of thep-type semiconductor layer 160 a. Thus, until the p-type semiconductorlayer 160 a is sufficiently etched, the etching process may beperformed; and control of the thickness of the p-type semiconductorlayer pattern 160 may be easily and accurately controlled.

In the etching process for forming the p-type semiconductor layerpattern 160, damage to the upper surface of the channel-supplying layer140 may be prevented as the top of the channel-supplying layer 140 iscompletely covered by the etch-stop layer 150.

As the p-type semiconductor layer pattern 160 is formed on a part of thechannel layer 130, a 2DEG region may not be formed on some parts of thechannel layer 130 on which the p-type semiconductor layer pattern 160 isformed; and the 2DEG region may be formed on the other parts of thechannel layer 130 on which the p-type semiconductor layer pattern 160 isnot formed.

Referring to FIG. 7E, the first passivation layer 174 may be formed onthe etch-stop layer 150 to cover the p-type semiconductor layer pattern160; and the second passivation layer 176 may be formed on the firstpassivation layer 174.

In exemplary embodiments, after the first passivation layer 174 isformed, the first passivation layer 174 is planarized until the top ofthe p-type semiconductor layer pattern 160 is exposed. Subsequently, thesecond passivation layer 176 may be formed on the first passivationlayer 174 and on the p-type semiconductor layer pattern 160.

Subsequently, a source electrode hole 182 p and a drain electrode hole184 p may be formed in the first and second passivation layers 174 and176, in the etch-stop layer 150, and in the channel-supplying layer 140and may expose the top of the channel layer 130. A gate electrode hole186 p may be formed in the first and second passivation layers 174 and176 to expose the top of the p-type semiconductor layer pattern 160. Forexample, the processes of forming the source electrode hole 182 p, thedrain electrode hole 184 p, and the gate electrode hole 186 p may be ahigh-frequency inductively coupled plasma reactive ion etching (ICP-RIE)process.

Referring to FIG. 7F, the source electrode hole 182 p and the drainelectrode hole 184 p may be filled with a conductive material to formthe source electrode 182 and the drain electrode 184 that are connectedto the channel layer 130.

The conductive material may include at least one of tantalum (Ta),tantalum nitride (TaN), tungsten (W), aluminum (Al), titanium (Ti), andtitanium nitride (TiN). For example, the source electrode 182 and thedrain electrode 184 may have a structure in which metal layers includingTa, Al, W, and TiN are stacked. However, the materials of the source anddrain electrodes 182 and 184 are not limited thereto; and the source anddrain electrodes 182 and 184 may include any material that may be inohmic contact with the channel layer 130.

Subsequently, heat treatment may be performed at a temperature of about500° C. to 600° C.

The gate electrode hole 186 p may be filled with a conductive materialto form the gate electrode 186 that is connected to the p-typesemiconductor layer pattern 160.

The HEMT device 100 is completely manufactured to perform theabove-described processes.

According to the method of fabricating the HEMT device 100, theetch-stop layer 150 may protect the top of the channel-supplying layer140 in the process of forming the p-type semiconductor layer pattern160. In addition, the etch-stop layer 150 and the channel-supplyinglayer 140 form a stable interface; and, thus, an on-resistance may beprevented from rising due to a surface charge trap and current collapsemay be minimized.

FIG. 8 is a schematic diagram of a power module system 1000 employing anHEMT, according to an exemplary embodiment.

Referring to FIG. 8, the power module system 1000 may include a poweramplifier module 1010 that includes HEMT devices 100 and 100 a to 100 daccording to exemplary embodiments of the present inventive concepts. Inaddition, the power amplifier module 1010 may be a radio frequency (RF)power amplifier module. The power module system 1000 may include atransceiver 1020 that is coupled to the RF power amplifier module 1010.

The RF power amplifier module 1010 may receive an RF input signal,RF_(in)(T), from the transceiver 1020 and may amplify the RF inputsignal, RF_(in)(T), to provide an RF output signal, RF_(out)(T), The RFinput signal, RF_(in)(T), and RF output signal, RF_(out)(T), maycorrespond to the transmitting mode of signals indicated by arrows inFIG. 8.

The amplified RF output signal, RF_(out)(T), may be provided to anantenna switch module (ASM) 1030 and may facilitate the over-the-air(OTA) transmission of the RF output signal, RF_(out)(T), through anantenna structure 1040. The antenna switch module 1030 may also receiveRF signals, RF(R), through the antenna structure and may couple thereceived RF signals, RF(R), to a transceiver, and these may correspondto the receiving mode of signals.

In exemplary embodiments, the antenna structure 1040 may includeunidirectional or multi-directional and/or omni-directional antennas.For example, the antenna structure 1040 may be a dipole, monopole,patch, loop, or microstrip antenna. In addition, the antenna structure1040 is not limited thereto but may include all kinds of antennas thatare suitable for the OTA transmission or for reception of RF signals.

The system may be a system including power amplification. For example,the power module system 1000 may be used for power amplification at ahigh frequency and for various purposes, such as a personalcommunication service, satellite communication, a radar system,broadcasting communication, and medical equipment.

One of ordinary skill in the art would recognize that the presentinventive concepts are not limited to the above-described embodimentsand to the accompanying drawings; and replacements, variations, andchanges may be made thereto without departing from the technical spiritof the present inventive concepts.

What is claimed is:
 1. A high-electron-mobility transistor devicecomprising: a substrate a plurality of semiconductor layers formed onthe substrate, wherein a two-dimensional electron gas (2DEG) region isformed in the semiconductor layers; an etch-stop layer formed on theplurality of semiconductor layers; a p-type semiconductor layer patternformed on the etch-stop layer; and a gate electrode formed on the p-typesemiconductor layer pattern.
 2. The high-electron-mobility transistordevice of claim 1, wherein the plurality of semiconductor layerscomprise a first semiconductor layer and a second semiconductor layerthat are sequentially formed on the substrate, and wherein the 2DEGregion is formed in a part of the first semiconductor layer adjacent toan interface between the first semiconductor layer and the secondsemiconductor layer.
 3. The high-electron-mobility transistor device ofclaim 2, wherein the 2DEG region is not formed in a part of the firstsemiconductor layer that overlaps with the p-type semiconductor layerpattern.
 4. The high-electron-mobility transistor device of claim 2,wherein the second semiconductor layer comprises a material having aband gap energy higher than that of the first semiconductor layer. 5.The high-electron-mobility transistor device of claim 2, wherein thefirst semiconductor layer comprises gallium nitride, and wherein thesecond semiconductor layer comprises aluminum gallium nitride.
 6. Thehigh-electron-mobility transistor device of claim 2, further comprisinga hole injection layer between the etch-stop layer and the secondsemiconductor layer.
 7. The high-electron-mobility transistor device ofclaim 1, wherein the p-type semiconductor layer pattern comprisesgallium nitride doped with p-type impurities or aluminum gallium nitridedoped with p-type impurities.
 8. The high-electron-mobility transistordevice of claim 1, wherein the etch-stop layer is in contact with anentire bottom surface of the p-type semiconductor layer pattern.
 9. Thehigh-electron-mobility transistor device of claim 1, wherein theetch-stop layer comprises silicon carbon nitride (Si_(x)C_(1-x)N), where0≦x≦1.
 10. The high-electron-mobility transistor device of claim 1,further comprising an n-type semiconductor layer between the p-typesemiconductor layer pattern and the gate electrode.
 11. Ahigh-electron-mobility transistor device comprising: a substrate; achannel layer formed on the substrate; a channel-supplying layer formedon the channel layer; an etch-stop layer formed on the channel-supplyinglayer; a p-type semiconductor layer pattern formed on a part of theetch-stop layer; and a gate electrode on the p-type semiconductor layerpattern.
 12. The high-electron-mobility transistor device of claim 11,wherein the etch-stop layer is formed on an entire top surface of thechannel-supplying layer.
 13. The high-electron-mobility transistordevice of claim 11, further comprising a source electrode and a drainelectrode that pass through the etch-stop layer and thechannel-supplying layer, and are connected to the channel layer.
 14. Thehigh-electron-mobility transistor device of claim 11, wherein the gateelectrode is formed to vertically overlap with the p-type semiconductorlayer pattern.
 15. The high-electron-mobility transistor device of claim11, wherein the p-type semiconductor layer pattern has a shapecorresponding to that of the gate electrode.
 16. A radio frequency poweramplifier module, comprising: a power amplifier module including atleast one high electron mobility transistor (HEMT), including: asubstrate a plurality of semiconductor layers formed on the substrate,wherein a two-dimensional electron gas (2DEG) region is formed in thesemiconductor layers; an etch-stop layer formed on the plurality ofsemiconductor layers; a p-type semiconductor layer pattern formed on theetch-stop layer; and a gate electrode formed on the p-type semiconductorlayer pattern; a transceiver coupled with the power amplifier module andconfigured to receive an input signal and to transmit the input signalto the power amplifier module, wherein the power amplifier module isconfigured to amplify the input signal received from the transceiver;and an antenna switch module coupled with the power amplifier module andincluding an antenna structure, wherein the antenna switch module isconfigured to receive the amplified input signal from the poweramplifier module and to transmit the amplified input signal over the airvia the antenna structure.
 17. The radio frequency power amplifiermodule of claim 16, wherein the antenna switch module is also configuredto receive the input signal through the antenna structure and totransmit the input signal to the transceiver.
 18. The radio frequencypower amplifier module of claim 16, wherein the plurality ofsemiconductor layers comprise a first semiconductor layer and a secondsemiconductor layer that are sequentially formed on the substrate, andwherein the 2DEG region is formed in a part of the first semiconductorlayer adjacent to an interface between the first semiconductor layer andthe second semiconductor layer.
 19. The radio frequency power amplifiermodule of claim 18, wherein the 2DEG region is not formed in a part ofthe first semiconductor layer that overlaps with the p-typesemiconductor layer pattern.
 20. The radio frequency power amplifiermodule of claim 18, wherein the second semiconductor layer comprises amaterial having a band gap energy higher than that of the firstsemiconductor layer.